Defined as fast-firing high-velocity automatic guns with calibres between 20mm and about 57mm, have been an integral part of the world's militaries for well over a century. A brief history of their development is given, followed by sections examining the basic principles of gun and ammunition design, including various unconventional systems. Next comes a survey of cartridges in calibre order, from 20mm to 57mm, including not only ammunition that has seen service, but also a wide range of experimental types. Finally there is a survey of the cannon, grouped by nationality, which again includes many experimental models.

The book includes data on about 200 different cartridges and 400 cannon, and has nearly 500 illustrations. It is the culmination of decades of research, and is unmatched in its coverage of this subject.